The present invention relates to a heat exchanger, which has a layered structure to carry out heat exchange between fluids for mainly air conditioning, and a method for preparing such a heat exchanger.
The latest development and popularization of air conditioning devices for heating and cooling, and the latest enlargement of living accommodations with air conditioning devices have given added importance to heat exchangers for air conditioning that can retrieve temperature and humidity in ventilation. As such heat exchangers have been widely used ones that have been disclosed in, e.g., JP-B-4719990, JP-B-5416054 and JP-B-512131. These heat exchangers have a basic structure wherein partitions having a heat-transfer property and moisture permeability are layered in multi-layered fashion at certain intervals, sandwiching each of spacers between adjoining partitions. The partitions are rectangular flat plates, and the spacers have a projected plane conformed to the partitions and are corrugated in a sawtooth or sinusoidal form. Each of the spacers is sandwiched between adjacent partitions so as to have a wave front thereof directed at 90xc2x0 or an angle close to this value with respect to the wave front of an adjacent spacer, providing two systems of fluid passages for alternately passing a first flow and a second flow in every other layer.
The characteristics that are required for partitions for a heat exchanger are low air-permeability and high moisture permeability. This is because fresh outdoor air taken indoors from outdoors is prevented from mixing with contaminated air exhausted outdoors from indoors in service and because vapor is required to transfer between the intake air and the exhaust air effectively in order to heat exchange sensible heat and latent heat simultaneously. As a material for partitions to meet the requirements has been developed a gas-impervious member as disclosed in JP-B-5846325. This member can be obtained by impregnating or coating a water-soluble polymer with lithium halide contained as an moisture absorbent into or on a porous member. As disclosed in JP-B-5334663, it has been devised to mix a guanidine type flame retardant in a water-soluble polymer and impregnate or coat the polymer into or on a porous member to improve flame retardance.
In a heat exchanger wherein a moisture-impervious member, which is prepared by impregnating or coating a water-soluble polymer into or on a porous member as stated, is used to provide each of partitions, it has been created a problem in that a part of the water-soluble polymer is melt due to moisture absorption into a partition to bring about a blocking phenomenon and to break a material for a partition during unwinding it for corrugation under conditions of high temperature and high humidity, such as in summer.
Such a heat exchanger is produced by corrugating a spacer material and almost simultaneously bonding the spacer material to a partition material to provide a single faced corrugated board unit as a heat exchanger constitute element and by putting the constituting elements one after another in multi-layered fashion.
Corrugation is carried out by a machine that mainly comprises upper and lower toothed corrugating rolls engaging and rotating together to shape a spacer material and a pressing roll to press the spacer material to a partition material in rotation. In order to provide the spacer material with proper corrugation, the upper and lower corrugating rolls and the pressing roll are normally maintained at a high temperature not lower than 150xc2x0 C. Since a portion of the water-soluble polymer in or on the partition material is melted by heat from the pressing roll at such a high temperature, the portion of the water-soluble polymer is apt to adhere to the pressing roll. If the temperature of the pressing roll is lowered, a spacer material can not be used as a heat exchanger constitute element due to improper corrugation though a partition material can be prevented from adhering to the pressing roll.
The temperature of the pressing roll and that of the upper and lower corrugating rolls have been controlled to a temperature hardly susceptible to melt and adherence and the feed speed is lowered so as to prevent the formation of improper corrugation up until now. A heat exchanger constituent element in the form of a single faced corrugated board unit may be warped by absorption of the moisture in air or by the moisture in a water-solvent type adhesive used in layering. In order to cope with these problems, a pressing operation has been carried out in the layering process and the bonding process to avoid the occurrence of a warp, which has made the processes quite complicated.
Since temperature exchange effectiveness is different from humid exchange effectiveness in such a type of heat exchanger because of the presence of difference heat exchange areas with respect to temperature exchange and humid exchange, the heat exchanger has created a problem in that enthalpy exchange effectiveness varies according to heat exchange under air conditions having different sensible heat factors, such as in summer and winter.
It is an object of the present invention to solve the problems, and to develop a method for preparing a heat exchanger capable of speeding up corrugation to enhance productivity, to develop a method for preparing a heat exchanger capable of speeding up corrugation to enhance productivity and of having flame retardance, to provide a heat exchanger capable of minimizing a difference in heat exchange effectiveness in summer and winter, and to provide a heat exchanger capable of making the production process simple and of reducing cost.
According to a first aspect of the present invention, there is provided a method for preparing a heat exchanger, comprising forming a moisture-permeable film having an air-impermeable function on a single side of a plate-shaped porous member to provide a gas-impermeable member for heat exchange, bonding a spacer corrugated for forming a fluid passage to a side of the gas-impermeable member with the moisture-permeable film formed thereon to provide a plurality of heat exchanger constituent elements, and layering the heat exchanger constituent elements so that the spacer in each of the heat exchanger constituent elements forms a fluid passage in each layer.
In the first aspect, the moisture-permeable film may be formed by chemical liquid coating or laminating.
According to a second aspect of the present invention, the porous member is made of a paper material, which has been subjected to flame retardant treatment.
In the second aspect, the moisture-permeable film may be formed by chemical liquid coating.
According to a third aspect of the present invention, the heat exchanger constituent elements are bonded together by an adhesive having a flame-retardant property.
The present invention also provides a heat exchanger, which is layered so as to have two systems of fluid passages in different layers, comprising a plurality of partitions for separating two systems of fluid passages, and a plurality of spacers corrugated for forming the fluid passages, wherein the partitions comprise a gas-impermeable member provided by forming an moisture-permeable film having an air-impermeable function on a single side of a plate-shaped porous member, and a spacer is bonded to a side of the gas-impermeable member with the moisture-permeable film formed thereon.
According to a fourth aspect of the present invention, one of the systems of passages is held by the spacers so that opposed partitions have the side of a partition with the moisture-permeable film formed thereon confronted to the side of the other partition with the moisture-permeable film formed thereon.
In the fourth aspect, the moisture-permeable film may be provided by chemical liquid coating or laminating.
According to a fifth aspect of the present invention, the partitions and the spacers comprise a material that has one side and the other side having different stretching properties with respect to humidity, and a side of the partitions that is apt to be easily stretched due to humidity is bonded to a side of the spacers that is apt to be easily stretched due to humidity.
In accordance with the first aspect of the invention, there is provided a method for preparing a heat exchanger capable of speeding up corrugation to enhance productivity.
In accordance with the second aspect of the invention, there is provided a method for preparing a heat exchanger capable of speeding up corrugation to enhance productivity and of having flame retardance.
In accordance with the third aspect of the invention, there is provided a heat exchanger having enhanced flame retardance in addition to the advantages offered by the first aspect or the second aspect of the invention.
In accordance with the fourth aspect of the invention, there is provided a heat exchanger capable of minimizing a difference in heat exchange effectiveness in summer and winter.
In accordance with the fifth aspect of the invention, there is provided a heat exchanger capable of making the production process simple and of reducing cost.